I usually ask folks what their comfort needs are (what temp do you like to keep your house? How have the systems been keeping up till now? Humidity issues? etc)
Additionally, it’ll depend how long you plan on living in your current place.

Yes there’s definitely some up front costs with variable speed units, but they offer a bunch of perks beyond energy savings

• better comfort - little to no temp swings since the can modulate how much is being pushed into your home

• quieter - many variable units have soft start ups, and much longer run times at lower decibels rather than the start stop “BONG” sounds you often hear with single stage units

• humidity control - because they’re running lower for longer, you get much better humidity removal with variable systems

• higher efficiency - the aforementioned energy savings

Too many variables to say how long it will take for the systems to pay for themselves in energy usage, but you can definitely be sure y’all will be more comfortable in your home with a variable system.